饲粮粗蛋白质水平对仔猪门静脉回流组织氮代谢的影响

Effects of Dietary Crude Protein Levels on Nitrogen Metabolism in Portal-drained Viscera of Piglets

本试验旨在研究饲粮粗蛋白质(CP)水平对仔猪门静脉回流组织(PDV)氮代谢的影响规律及机制。试验选用18头出生日龄接近的健康杜×长×大三元杂交猪(20±1.0)kg,分别安装门静脉、颈动脉、肠系膜静脉和肝静脉血插管,采用单因子完全随机设计分配到日粮赖氨酸、蛋氨酸、苏氨酸和色氨酸水平一致而CP水平分别为20.0%(对照)、17.0%和14.0%的3组饲粮中。1周后通过血插管采集血液样品,离心获取血浆,用于分析血浆中排流物质的浓度。结果表明:仔猪门静脉、肝静脉和肝动脉葡萄糖(GLU)浓度不受饲粮CP水平的影响(P>0.05),而门静脉GLU的净流量以及肝脏GLU的消耗量皆随饲粮水平的降低而显著降低(P<0.01);仔猪肝脏总蛋白(TP)的产量不受饲粮CP水平的影响(P>0.05);14.0%CP组仔猪肝脏尿素氮(UN)的产量显著低于对照组(P<0.05)。平衡4种重要必需氨基酸的情况下降低饲粮蛋白水平降低了肝脏UN的生成量,但是并未降低肝脏UN生成量与蛋白质采食量的比值。

This study was conducted to investigate the effects of dietary protein levels on nitrogen metabolism in the portal-drained viscera （PDV） of piglets. Eighteen healthy Duroc × Landrace × Yorkshire （DLY） piglets （20±1. 0 kg） were fitted with permanent catheters in the mesenteric vein, portal vein, hepatic vein, and carotid artery, and randomly allocated to receive one of three diets （6 piglets per treatment）, in which the levels of lysine, methionine, threonine and tryptophan were consistent while the designed CP content were 20.0% （control）, 17.0%, and 14. 0%, respectively. After one week of surgery recovery, blood samples from catheters were collected for determining the concentrations of nutrients. The results showed, there were no difference in glucose （GLU） concentration in the portal vein, hepatic artery and hepatic vein among three groups （P〉0.05）, but the net portal flux of GLU and the consumption of GLU in the liver were significant decreased in response to the reduction of dietary CP content （P〈0.01）; the production of total protein （TP） in the liver were not affected by the dietary CP content （P〉0.05）; the number of urinary nitrogen （UN） produced in liver of piglets fed diet with 14.0% CP content were significantly lower than that of the piglets in control group （P〈0.05）. Thus, it can be concluded that reducing dietary CP content supplemented with certain essential AA decreased the production of UN in the liver, however, this nutritional regulation did not decline the ratio of the production of UN in liver to protein intake.